The present invention relates to tools used on power machines and in particular to a novel knurling tool for use on such machines.
Various types of knurling tools, well known in the art, have been used extensively to impress or cut a plurality of grooves in the surface of a workpiece such as bar stock to provide a clip free gripping region along a portion of the bar stock.
Knurling tools have generally been comprised of a jaw-like structure having a base member to which a pair of outwardly extending knurl bit holding members were mounted, in either a movable or immovable manner, to form the jaw-like support structure. Knurling bits were then mounted in the ends of the outwardly extending members. In use bar stock can be fed frontally into the open end of the jaw-like support structure between the knurling bits. Apparatus is then provided to close the outwardly extending members about the end of the bar stock with the knurling bits exerting force against the surface of the bar stock. In an alternative arrangement the bar stock is rotated 90 degrees and fed sideways between outwardly extending members of the jaw-like structure. Thus, the outwardly extending members effectively "bite" around the bar stock along its length. In both arrangements the knurling bits are rotatably mounted in the end portions of the outwardly extending members.
In use, the knurling bits are clamped about the bar stock to exert force against the surface of the bar stock. As the bar stock is rotated, the knurling bits cause a grooved impression to be made in the surface of the bar stock. Thus, whether the knurling tool is a side feed or an end feed type of tool, the knurling bits must be forced against the surface of the bar stock with a substantial force in order that the surface of the bar stock will be impressed with the grooves.
A significant disadvantage of such jaw-like structures has been that the large forces required to make an impression in the surface of the bar stock, particularly when the stock is a hardened steel or other very hard substance, is that the substantial inward forces required to press the knurl bits against the bar stock cause the outwardly extending members to react so that they are forced apart slightly. This slight opening when the large force is applied can cause an improper or undesirable knurling pattern on the surface of the bar stock. In addition, the large forces required frequently cause the bearings of the machine to experience rapid wear.
In order to solve the problem of the jaw opening as the knurling bits are tightened against the surface of the workpiece, various techniques have been tried. The most common has been to simply provide a very rigid jaw-like structure where the forces necessary to open or widen the jaw-like members would be much greater than the force expected to be exerted by the knurling bits against the surface of the bar stock. However, the materials required to be used in making such a rigid structure make the resultant knurling tool quite expensive and quite large.
The present invention overcomes these disadvantages by providing a planar base member with an orifice through which the bar stock is fed. Knurling bits are mounted in planar slots provided in the planar face plate. The knurling bits then extend into the orifice and may be tightened against the surface of the workpiece by tightening screws movable in the plane of the face plate, which exert an inward force against the back of the knurling bit to force the knurling bit towards the center of the orifice and thus against the surface of the bar stock. As used herein, the plane of the planar base plate is a plane having a thickness which is approximately equal to the thickness of the face plate member.